I am first appologizing that my answers are long but I feel that this is an important subject.
Miketsp, now I’m going to disagree. I’m approaching this question from the point of view that every certifying agency concedes that “every dive you make puts you at risk, even when everything is done right.” Quite frankly, not enough is known about diving, and why complicate things with possible problems. Going back under the water starts to complicate things. Can it be done, sure? Should it be done? Let’s look at a few things:
Since I am a NAUI Instructor I’ll use NAUI text and information (this is what I am most familiar with). In Chapter 4 on Diving Science in the O/W book it states three steps to help in preventing DCS. 1) Staying within the time limits of the tables, 2) always ascend at a rate no faster than 30’/min. and 3) the third step in preventing DCS is to always perform a precautionary decompression stop at 15’ for 3 to 5 minutes.
I realize that uploading of N2 takes time and certain compartments (tissues) take in N2 at different rates. If the pressure is constant ingassing occurs rapidly at first and then slows down until your body reaches equilibrium many hours later. It then takes many hours to outgas completly. We control this ingassing by regulating our pressure and time. “Don’t stay down too deep, too long and come up too fast.” Besides pressure and time some other things to consider to help avoid suffering DCS – dehydration, temperature, fatigue, injuries, hard work before, during or after the dive, drugs, alcohol, obesity, age, going to altitude after diving, etc.
From the NAUI Master Diver certification book Chapter 4: Diving Physiology-
“If you stay too long and ascend too quickly at depth, inert gas (mostly N2) that you absorb can come out of solution and form small bubbles in your body.” “It is not likely to be the case that every dive makes bubbles in your body.” But, later on in this paragraph it is stated “susceptibility to DCS varies with individuals.” So, more potential problems putting a diver at risk?
Using the NAUI dive tables and assuming this is the first dive of the day a 60’ dive for 30 min. translates to an “F” diver. PADI you’re an “L”, SSI and Navy you’re also an “F”, others you’ll have to do the conversions. You’ll have N2 in your body. How much? I guess it varies by individual, but it warrants a SIT time.
Let’s get back to the original question about the diver shooting to the surface that may or may not be in trouble. You go to the surface, and there is a problem with this diver, is he your dive buddy? If not, where is your buddy? – I would think everyone would see this as a potential problem.
Let’s say that the diver in trouble was your buddy. You now do a tank tow and bring your buddy to the boat; you assist the crew with getting him back onto the boat. You now jump back in the water to do your safety stop (because you think you have too much nitrogen in your system - maybe not much – but, how much is too much? And if you don’t think you have too much N2, then why are you going back into the water?). Hopefully, you told the crew what you are doing.
You now are the last one in the water. Let’s say something did happen to you. We don’t know for sure that something could happen, but we have to concede that it is possible why? because all individuals are different and not enough is known about diving. You now black out and sink to the bottom why? because you ran 5 miles before the dive, went in the hot tub to relax your throbbing muscles and forgot your water bottle back in the car. In your excitement and haste you forgot to put any air in your BC and you always dive a little over weighted to stay down.
The boat crew was so preoccupied with the rescue of your dive buddy with giving O2, first aid, collecting statements, securing gear, calling the Coast Guard, filling out forms, their stress levels going through the roof, they forgot about you. After about 15 or 20 minutes someone remembers that there was this other diver. Where did he go?
So, not all of the problems with going back underwater have to do with the formation and alleviation of bubbles, whether instantaneous or not or what size they become a problem, or wether they even developed. Different people will react differently. There are no assurances in diving. No one can say for sure that it is safe for you to go back into the water. Me, I’ll take my chances on the surface. And, I’ll instruct my students to do the same.
